Many waters contain contaminants that can present a hazard to people or the environment, or make further processing, such as evaporation or reverse osmosis more difficult. Membrane filters are commonly used to remove such contaminants. Membrane elements are typically made of polymers or ceramics, both of which are frequently placed inside a pressure vessel to contain the pressurized fluid to be treated. The element and pressure vessel combination are referred to as membrane modules or modules. Such pressure vessels also provide separate ports to allow a feed to enter the module, filtrate to exit after being processed through the membrane, and a retentate chamber for removal of the filtered material.
Ceramic membranes that are commonly used have a multilayer structure with a relatively high permeability support, and a thinner separation layer which enables the separation by passing some components (typically water and small solutes) while retaining others. To increase surface area, a number of channels or capillaries are typically present in the support, each with a coating. During use of the membrane, feed enters these capillaries before passing through the membrane into the support structure. To keep feed from passing directly into the support on either end, a face end seal layer is used to prevent transport through the ends. Commonly used materials for face end seals include epoxies, polyurethanes, and glass. In comparison to the other components in a ceramic membrane module, this face end seal is particularly sensitive to mechanical damage due to both the material properties of the face end seal, and the fact that housings which have been used to date leave the face end seal at the end of the housing, preventing it from serving as shielding.